Aircraft based cellular system

ABSTRACT

An apparatus and method for providing an aircraft-based wireless communications service is disclosed. An exemplary system includes a plurality of aircraft each including on-board equipment for supporting wireless communications with one or more dual mode handsets and for exchanging wireless communication traffic and control information. One or more ground stations communicate with the plurality of commercial aircraft using feeder communications links exchanging the wireless communication traffic and control information and providing interfaces with a terrestrial telecommunications infrastructure. A control center manages the one or more ground stations and the on-board equipment of the commercial aircraft and dynamically assigns resources to the on-board equipment of the plurality of aircraft using an overlapped set of coverage patterns.

BACKGROUND OF THE INVENTION

[0001] 1. Field of the Invention

[0002] The present invention relates to radio communication systems, andparticularly to cellular radio communication system using aircraft.

[0003] 2. Description of the Related Art

[0004] In the United States and elsewhere, domestic cellular telephonycoverage is not universally available. Estimates suggest that coverageby terrestrial cellular systems using analog (first generation or 1G)technology now extends to 70% of the co-terminus United States land massand 95% of the population. Likewise, coverage by terrestrial systemsusing digital (second generation or 2G/2.5G) technology extends to only20% of the co-terminus United States land mass but includes 80% of thepopulation.

[0005] Within those geographical areas already covered by terrestrialcellular service, vagaries of electromagnetic propagation cause gaps inservice with estimates indicating that these gaps are as extensive as10% to 20% of nominal coverage. As it requires a significant investment,further expansion of the existing terrestrial cellular infrastructure toaccommodate the population not presently served is unlikely.

[0006] Furthermore, when deployed in terrestrial cellular systems,anticipated third generation (3G) technology will likely cover aco-terminus United States land mass no larger than its immediate 2G/2.5Gpredecessor. Some authors refer to these shortfalls in terrestrialcellular coverage as the cellular divide or, for generations 2G andbeyond, the digital divide.

[0007] Prior inventors have brought forth a variety of approaches forproviding coverage of mobile telephony users in areas not presentlyserved. Most well known are low earth-orbiting (LEO) satellite-basedsystems such as Iridium and Globalstar. These systems rely on aconstellation of LEO satellites to provide coverage for properlyequipped users. The users communicate directly with a satellite, whichuses feeder links to relay user traffic to a ground station, or groundstations, for connection with the terrestrial telecommunicationsinfrastructure. Low earth orbiting satellites necessarily provide globalor near-global coverage so that the associated investment yields anoverall capacity, which greatly exceeds the capacity available fordomestic (US) usage at any time.

[0008] Also presently in service are several geosynchronous (GEO)satellite-based systems, e.g. MSV, Thuraya and ACeS. These systems placea dedicated satellite (or satellites) above the geographic region to becovered so that their entire capacity is available to properly equippedusers therein. Users again communicate directly with the satellite,which relays traffic to a ground station using feeder links.

[0009] For either LEO or GEO satellite-based systems, some userequipment also operates with selected terrestrial cellular systems.However, not all user equipment supports dual mode operation, e.g., MSVoffers only dedicated single mode user equipment.

[0010] Alternate satellite-based systems are also possible. For example,U.S. Pat. No. 5,722,042, which is incorporated by reference herein,advocates a satellite communications system with a double-layeredearth-orbiting constellation with a lower first orbit altitude and ahigher second orbit altitude. None of these alternate systems appears tohave entered service.

[0011] Regardless of their orbital characteristics, satellite-basedsystems opt to impose a fixed set of cells on the earth's surface. Thisapproach forces non-stationary satellites to adjust their antennas totrack a coverage area as they move along their orbits and to rapidlyswitch their antennas between coverage areas periodically to support anew coverage area on the earth's surface. Supporting such fixed patternssimplifies user operation but complicates antenna design and increasessatellite cost.

[0012] High costs associated with rocket launches make satellite-basedsystems very expensive to deploy. Moreover, high usage costs and bulky,expensive user terminals limit adoption of deployed satellite-basedsystems by potential subscribers. Several of these systems have gonethrough bankruptcy whereas others only recently entered service withfinancial results still indeterminate.

[0013] Other systems for providing coverage of domestic mobile telephonyusers in unserved areas include a variety of elevated platforms,including an interesting dual use of National Weather Service balloons.

[0014] U.S. Pat. No. 3,742,358, which is incorporated by referenceherein, and other patents cited therein illustrate the distant originsof knowledge of extensive coverage associated with elevated platforms,e.g., airborne platforms. Subsequently, U.S. Pat. Nos. 4,704,732 and5,104,059, which are both incorporated by reference herein, identifycommunications as one application of freely suspended, long endurancehigh altitude platforms. U.S. Pat. Nos. 4,476,576 and 4,903,036, whichare both incorporated by reference herein, employ a tethered aerostatspecifically as an antenna to support VLF communications.

[0015] U.S. Pat. Nos. 5,949,766 and 6,151,308, which are bothincorporated by reference herein, describe ground devices and anelevated wireless communications hub capable of switching, i.e.,separating signals from multiple sources and sending them to multipledestinations. U.S. Pat. No. 5,963,877, which is incorporated byreference herein, extends this concept to high altitude platforms thatemploy antennas capable of creating a cell structure on the earth'ssurface to support wireless communications including cellular telephony.U.S. Pat. No. 6,061,562, which is incorporated by reference herein,further extends this concept to include a dedicated aircraft flyingabove the service region while U.S. Pat. No. 6,167,263, alsoincorporated by reference herein, uses a plurality of dedicated aerialplatforms or vehicles, capable of communicating with each other, toprovide a global communications network. Finally, U.S. Pat. No.6,324,398, which is incorporated by reference herein, explicitlyemulates the terrestrial cellular infrastructure with ground-basedswitching centers supporting base stations located on a plurality ofdedicated airborne platforms.

[0016] All of the foregoing systems strive to keep their elevatedplatforms stationary over a fixed geographic area to support a fixedservice area or set of fixed service areas. In line with this objective,powered elevated platforms rely on tracking antennas much like low earthorbiting satellites but they do not utilize handover of coverage areasas these satellites do.

[0017] At present, none of these systems related to elevated, butnon-orbiting, platforms has entered operational service. As revenue thatthey generate must cover all operating costs, nationwide deployment of acellular-type system comprising dedicated elevated platforms appearsunlikely. As intended applications, systems based on elevated platformsmost often describe either supplemental cellular coverage in regionswith heavily utilized terrestrial cellular infrastructures or primecoverage in heavily populated areas with limited or no terrestrialcellular infrastructure. They do not discuss sparsely populated regionsbecause operation therein does not admit recovery of said platform'soperating costs.

[0018] Commercial aircraft offer another set of elevated platforms thatcan provide wireless communications to remote terrestrial users. Sincethese platforms are airborne and, hence, positioned to offer wirelesscommunications services, for the primary purpose of transportingpassengers or freight, wireless communications services must defray onlya minor part of an commercial aircraft's operating cost. In addition,commercial aircraft pass over remote areas even though they fly betweenpopulation centers. With more than 1500 commercial aircraftsimultaneously airborne for more than sixteen hours daily, domesticcoverage provided by this fleet is extensive.

[0019] A few years ago, many commercial airlines began offering airborne(on-board) telephone services by implementing telephone units atspecific locations within the cabin of the commercial aircraft,typically placed in seatbacks. This service used UHF frequency bands tolink outbound calls (from passengers) to ground stations but, due tohigh usage costs, never achieved financial success. Such servicesinvariably do not support inbound calls because ground-based callersencounter prohibitive difficulties in identifying a ground stationwithin transmission range of a particular aircraft. Because ofdisappointing financial results, some airlines are now removing thisequipment to avoid the cost associated with transporting its weight.

[0020] Several subsequent inventions address shortcomings of airbornetelephone services. For example, U.S. Pat. No. 5,651,050, which isincorporated by reference herein, describes a method for directing callsof terrestrial origin to an on-board telephone or telephones withoutknowing aircraft location. The on-board telephones are dedicated to theaircraft but may be temporarily assigned to passengers using traveleridentification numbers.

[0021] U.S. Pat. No. 6,052,604, which is incorporated by referenceherein, extends this calling method to allow passengers to use their ownsubscriber identity module (SIM) cards as identifiers while sharingon-board telephone resources. This method invokes the system securityassociated with SIM cards without requiring dedicated telephone unitsfor each passenger who wishes to avail themselves of outbound and/orincoming calling services.

[0022] Although Global System for Mobile Communications (GSM)communications equipment employs SIM cards, neither TDMA nor CDMAequipment do. Re-use of passenger equipment offers a powerful incentiveto adoption of airborne telephony service, however. Thus, U.S. Pat. No.6,249,913, which is incorporated by reference herein, describes a methodto use passengers' personal terrestrial cellular telephones with dockingcradles that disable on-the-air transmissions from these units withinthe aircraft. Contrariwise, U.S. Pat. No. 6,249,243, which isincorporated by reference herein, describes a method for using lowpower, on-the-air transmissions to and from passengers' personalcellular telephones within the aircraft.

[0023] U.S. Pat. No. 6,393,281, which is incorporated by referenceherein, describes a means for seamless handoff of calls as an aircraftpasses out of the coverage area of one ground station and into thecoverage area of another ground station.

[0024] Although focused on providing broadband services to passengers,U.S. Pat. No. 6,285,878, which is incorporated by reference herein,initially recognized the feasibility of extending these airborneservices beyond passengers to include terrestrial users located withinline-of-sight of the host aircraft. The method described in this patentis more restrictive than that described herein because it relies oncrosslinks between commercial aircraft and requires control overaircraft scheduling to ensure availability of platforms for relayingcommunications traffic.

[0025] In addition, crosslink equipment is expensive especially as itrequires pointing and supports multiple levels of relay, i.e.,communications traffic from multiple aircraft. Airlines set theirschedules based on attracting passengers within constraints imposed bytheir specific gate assignments at particular airports, which may notreadily support long strings of aircraft relaying communications trafficas, for instance, those crossing the North Atlantic Ocean.

[0026] Although others have observed that commercial aircraft andcellular telephony make a potent combination, none have addressedcoverage gaps that inevitably develop in terrestrial cellular patternshosted by commercial aircraft. See e.g., V. Pandiarajan and L. Joiner,“Undedicated HAAP Based Architecture for Cellular Data Transfers,” IEEESoutheastcon, pp. 23-26, 2000, which is incorporated by referenceherein. As these aircraft choose their own schedules and flight dynamicswhile operating in an environment that sometimes disrupts both schedulesand/or flight dynamics, using commercial aircraft to offercost-effective wireless communications services requires techniquesdescribed in the present invention.

SUMMARY OF THE INVENTION

[0027] The present invention uses commercial aircraft as cellular sitesto provide wireless communications for terrestrial users within aircraftfield of view and for passengers. The plurality of commercial aircraftin flight at any given time provides extensive geographic coverageincluding areas currently unserved or underserved by terrestrialcellular systems. Use of dual mode user equipment and moving,overlapping cellular structures admits simple and inexpensive on-boardequipment for aircraft.

[0028] A typical embodiment of the invention encompasses a system forproviding aircraft-based wireless communications service to terrestrialsubscribers, especially in areas lacking cellular coverage or in gaps inexisting terrestrial-based cellular coverage, and also to passengerson-board these aircraft. The system includes a plurality of commercialaircraft serving as base stations with on-board equipment capable ofsupporting wireless communications with properly equipped users and ofexchanging traffic and control information with ground stations. Groundstations are provided that communicate with the commercial aircraftusing feeder communications links to exchange traffic and controlinformation and also to provide interfaces with the terrestrialtelecommunications infrastructure. A control center manages groundstations and commercial aircraft serving as base stations anddynamically assigns resources to the aircraft using an overlapped set ofcoverage patterns. Dual mode handsets are capable of communicating withthe aircraft on-board equipment using wireless communications, eitherinternal or external to the aircraft and with standard terrestrial-basedcellular service when available.

[0029] The wireless communications service can be a cellular-typeservice where the cellular-type links use standard cellularcommunications. Furthermore, the wireless communications links canemploy cellular standards and technology but operate in frequency bandsnot allocated to other terrestrial cellular systems. In order to preventpassengers from using terrestrial cellular equipment while in flight,the system can also include a means for on-board jamming of terrestrialcellular bands. Crosslinks can also be employed between commercialaircraft for exchanging user traffic and control information. The groundstations can be collocated with cellular sites and the control centercan be either ground-based or satellite-based.

[0030] The system can employ overlapped coverage patterns as a set ofcellular patterns. These overlapped coverage patterns can be based on aprimary aircraft direction of travel. The feeder communications linkscan operate at microwave or millimeter wave bands, also utilizingcellular-type communications.

[0031] It is an object of the present invention to provide wirelesscommunications service for presently unserved or underserved terrestrialusers using commercial aircraft as communications base stations. It is afurther object of the present invention to provide wirelesscommunications service for passengers on the same commercial aircraft.As detailed hereafter, these and other objects are met by the presentinvention.

BRIEF DESCRIPTION OF THE DRAWINGS

[0032] Referring now to the drawings in which like reference numbersrepresent corresponding parts throughout:

[0033]FIG. 1 is a block diagram showing the principal components of apreferred embodiment of the system of the present invention;

[0034]FIG. 2 shows a ground coverage cell for serving terrestrial usersas it moves along with its host aircraft during flight;

[0035]FIG. 3 shows a cellular pattern provided by multiple aircraftwhere each aircraft supports one coverage cell on the ground;

[0036]FIG. 4 shows the structure of overlapping northbound, eastbound,southbound and westbound cellular patterns;

[0037]FIG. 5 shows an aircraft-based directional cellular patternproviding domestic coverage;

[0038]FIG. 6 shows re-use of neighboring or adjacent frequencyallocations within an aircraft for passenger services;

[0039]FIG. 7 shows sectorization of each coverage cell into multipleparts including multiple embodiments that use two, four or sevensectors, respectively;

[0040]FIG. 8 shows the cellular pattern structure for ground stationfeeder links between aircraft and ground stations;

[0041]FIG. 9 shows a ground station with feeder links serving fouraircraft comprising one aircraft from each of the four aircraft-baseddirectional cellular patterns;

[0042]FIG. 10 shows a ground station with feeder links serving twoaircraft that share an allocation thereby providing a joint coveragecell;

[0043]FIG. 11 shows an aircraft switching its feeder link between twoground stations; and

[0044]FIG. 12 is a flowchart of an exemplary method of the invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

[0045] In the following description of the preferred embodiment,reference is made to the accompanying drawings which form a part hereof,and in which is shown by way of illustration a specific embodiment inwhich the invention may be practiced. It is to be understood that otherembodiments may be utilized and structural changes may be made withoutdeparting from the scope of the present invention.

[0046] 1. Overview

[0047] There are typically over 3000 commercial aircraft operating overthe United States during normal daily operating hours. Operating ataltitudes above 30,000 feet, these aircraft have a field of view toearth of over 200 miles, and as a result, these aircraft offer anexcellent platform for wireless communications towers that can providedigital wireless communications coverage over most of the United States.In addition, aircraft equipped with wireless communications capabilitycan also provide digital wireless communications services (such ascellular telephony) to onboard passengers.

[0048] The system architecture of the present invention utilizesaircraft equipped with base stations that operate as wirelesscommunications towers which form a cellular structure that migrate withthe aircraft. Therefore, the cellular frequency re-use pattern “moves”with the aircraft. All aircraft equipped with wireless communicationswill provide digital communications for the onboard passengers. Theonboard wireless communications are routed to the terrestrialtelecommunications infrastructure (may be existing) through wirelesscommunication links established with ground stations for backhaulcommunications. Some of the equipped aircraft are designated to provideservice to terrestrial users and are assigned a cellular frequency thatmigrates with the aircraft. As these aircraft traverse above terrestrialusers, the aircraft acts as a base station for the terrestrial user,routing the terrestrial users communications through the aircraft basestation to the ground station for backhaul communications.

[0049] Those aircraft assigned cellular frequencies form a floatingcellular frequency structure that repeats over and over again asselected aircraft are assigned cellular frequencies. The cellularstructure not only repeats linearly along the flight path of theselected aircraft but also perpendicularly to these flight paths. Thisis done to minimize the number of frequencies used and thus maximize thefrequency re-use.

[0050] By maximizing frequency re-use, a greater number of terrestrialusers may be served within an allocated frequency band. In order tooptimize frequency re-use, a ground-based control center coordinates theallocation of cellular frequencies assigned to the selected equippedaircraft. The control center ensures that the aircraft assigned a givencellular frequency does not interfere with the cellular frequencyassigned to a neighboring aircraft for purposes of servicing terrestrialusers.

[0051] The control center ensures proper assignments of the movingcellular structure and reassignments of the cellular frequencies from anexisting assigned aircraft to another equipped aircraft as may benecessary to ensure the integrity of cellular structure as the aircrafttraverse their respective flight path. The system will provide serviceto user with terminals that are equipped with appropriate functionalityto operate with the wireless base stations aboard the equipped aircraft.Users on the ground with terminals implemented with this capability canobtain digital wireless communications services within those landmassareas presently underserved. Aircraft passengers with these terminalscan obtain digital wireless communications during flight onboardaircraft equipped with base stations. It is envisioned that these userterminals would also offer standard wireless communications via existingcellular communications infrastructures.

[0052] The system architectural approach utilizing current wirelesstechnology described herein offers an economical means of providingdigital wireless communications coverage in the range of 90 to 95% ofdomestic landmass that encompasses a population in the range of 98 to99%.

[0053] 2. Exemplary Embodiments

[0054] A typical embodiment of the invention includes an implementationbased on commercial passenger aircraft, a nationwide grid of groundstations, centralized system control, dual mode user equipment, and afrequency allocation distinct from the standard terrestrial cellularfrequency bands. It is recognized that the principles of the presentinvention apply with other air vehicles or a mix of aircraft and otherair vehicles, with distributed system control, with regional groundstation grids, with user equipment that supports more than two modes ofoperation, and with multiple (more than one) frequency allocationsdistinct from the standard terrestrial cellular bands.

[0055]FIG. 1 provides a block diagram for the commercial aircraft-basedsystem 101 comprising three segments (aircraft 103, user 105 and control107) and the interfaces between these segments. The exemplary systemuses commercial aircraft 109, 111 to provide wireless communications forterrestrial users 113, 115 within aircraft field of view andcollaterally for on-board users 117 (e.g., passengers). The plurality ofdomestic commercial aircraft airborne at most times provides extensivegeographic coverage including areas currently without service orunderserved by terrestrial cellular systems. Thus, these commercialaircraft serve a dual use and are not dedicated only to operation of thesystem 101.

[0056] The aircraft segment 103 includes commercial aircraft 109, 111serving as base stations with on-board equipment capable of supportingwireless communications with properly equipped users 113, 115, 117 andof exchanging traffic and control information with ground stations 119using feeder communications. This segment need not include all domesticcommercial aircraft, but to provide extensive domestic coverage moreaircraft than any single domestic airline currently operates should beemployed.

[0057] The user segment 105 comprises subscribers (terrestrial 113, 115or on-board 117) and equipment (dual mode handsets 121, 123, 125 andancillary equipment such as docking stations, chargers and batteries).User equipment 121, 123, 125 can communicate with aircraft on-boardequipment using cellular-type wireless communications either external127, 129 or internal 131, 133 to the aircraft. Dual mode user equipment121, 123, 125 can also communicate with standard terrestrial-basedcellular service wherever available except on-board a host aircraft inflight where techniques such as low level jamming can be used topreclude use of terrestrial-based cellular service. This servicespecifically addresses individuals lacking cellular service as potentialusers. Current cellular subscribers and frequent flyers also presentpromising candidates.

[0058] The control segment 107 includes a grid of one or more groundstations 119 spread across the entire system coverage area (similar toterrestrial cellular base stations) and a control center 135. Groundstations 119 communicate directly with commercial aircraft 109, 111using feeder communications links 137, 139 to exchange traffic andcontrol information and also to provide backhaul interfaces 141 with theterrestrial telecommunications infrastructure. Collocation of groundstations with existing cellular sites is not mandatory but does offer aready-made terrestrial infrastructure as these sites experienceidentical connectivity requirements.

[0059] The control center 135 monitors all ground stations 119 andcommercial aircraft 109, 111 serving as base stations and assignsresources to them. These assignments are dynamic to accommodate aircraftmovement and changes in aircraft schedules, so this control center mustperiodically convey assignments to aircraft.

[0060] Interfaces between the segments include cellular-type links 127,129 between users and aircraft and feeder links 137, 139 betweenaircraft and ground stations. To avoid interference, neither of theseinter-segment interfaces uses terrestrial cellular operatingfrequencies. Within segments, terrestrial interfaces 143 exist betweenground stations 119 and the control center 135. In further embodiments,crosslinks 145 between aircraft can be used as a natural extension ofthe present invention.

[0061]FIG. 2 shows an exemplary individual coverage cell 201 on thecontinental U.S. supported by a host aircraft 203 at a particular time.One key to simple aircraft antennas and inexpensive aircraftinstallations is a cellular pattern comprising coverage cells that movealong with their respective host aircraft. As this aircraft continues inflight, its coverage cell moves along with it. Thus, when this aircraftsubsequently arrives at position 205, its coverage cell 207 now occupiesa different geographical area. Later in its flight, when this aircraftarrives at position 209, its coverage cell 211 now occupies yet anothergeographical area. Other host aircraft also support coverage cells,which migrate along with their hosts in the same fashion.

[0062]FIG. 3 shows coverage cells from different host aircraft forming acellular pattern 301 on the ground. This figure employs a re-use factorof four wherein cells 303, 305, 307 and 309 use a first set of allocatedfrequencies, cells 311, 313, 315 and 317 use a second set of allocatedfrequencies, cells 319, 321, 323 and 325 use a third set of allocatedfrequencies, and cells 327, 329, 331 and 333 use a fourth set ofallocated frequencies. Although cellular patterns with a re-use factorof four provide optimal performance for voice applications (e.g., R.Rudokas, “Cellular System Performance Prediction,” Radio and WirelessConference, pp. 153-156, 1998, which is incorporated by referenceherein), embodiments of the invention can employ other re-use factors aswell.

[0063] Coverage cell size is a critical factor in system design. Largercells require fewer aircraft to provide full domestic coverage, butplace more stress on user equipment making these units more expensive.For example, commercial aircraft operating at approximately a 30,000foot altitude enjoy a line of sight exceeding 200 miles so many choicesof cell size are possible. See e.g., B. El-Jabu and R. Steele, “CellularCommunications Using Aerial Platforms,” IEEE Transactions on VehicularTechnology, pp. 686-700, May 2001, which is incorporated by referenceherein. One embodiment of the present invention compromises by selectingapproximately 43 miles as a coverage cell radius. For hexagonalplacement of coverage cells, maximum inter-cell overlap is approximately11.6 miles. Thus, approximately 74.4 miles separates adjacent cellcenters in each direction. Each cell covers approximately 5809 (π×432)mi² of which about 17% is lost to overlaps, yielding an effectivecoverage area of 4821 mi² per cell. So, approximately 568 cells of thissize can provide complete U.S. domestic coverage.

[0064] As each coverage cell moves along the ground with its assignedaircraft, a specified aircraft may keep its allocated frequencies, i.e.,its cell intact from point of origin to destination although it may notsupport ground-based traffic at all times. Providing allocations toaircraft is an important task executed by the control segment, whichmust ensure that these cells maintain coverage without interfering withone another.

[0065] Commercial aircraft have different points of origin and differentdestinations so coverage cells hosted by different aircraft do notnecessarily support a highly structured cellular pattern as familiarfrom terrestrial cellular systems. Instead they exhibit cellularpatterns with dynamic variation especially for aircraft traveling indifferent directions. As indicated in FIG. 3, if all participatingaircraft travel in the same direction 335 (westbound as shown), then theresulting cellular pattern holds its shape for more than the few minutessufficient to alter a pattern that relies on counter-directionalaircraft.

[0066] Consequently, to mitigate effects of aircraft schedules anddynamics on cellular re-use patterns, the present invention can separateaircraft into four groups corresponding to their primary directions oftravel. Directions selected do not need to correspond to the cardinaldirections (northbound, eastbound, southbound and westbound). Employingseparate cellular patterns for each group minimizes significantdifferences in aircraft ground velocity due to the jet stream and theirdirection of travel thus enabling formation of more stable cellularpatterns. Deployment of this system does not require all four of thesepatterns; even a single directional pattern can provide service.However, coverage improves with each directional pattern added.

[0067]FIG. 4 shows a frequency allocation split into four cellularpatterns 401, 403, 405, 407 assigned to northbound 409, eastbound 411,southbound 413 and westbound 415 aircraft flows, respectively. Asillustrated in FIG. 4, each of these four directional cellular patternsemploys a re-use factor of four internally. Other choices of re-usefactor are possible and cell patterns assigned to different directionsof travel may also choose to employ different re-use factors.

[0068]FIG. 5 shows that as the number of aircraft in flight permits,each directional cellular pattern provides nationwide coverage for thewestbound cellular pattern 501. Aircraft movement and schedules causetemporary gaps in coverage in any of these directional cellularpatterns. Use of overlapping directional patterns reduces the incidenceof coverage gaps and decreases their durations. See e.g., R. Rudokas,“Capacity Losses in Sector and Microcell Cellular Systems,” IEEECommunications Letters, pp. 43-45, March 1997, which is incorporated byreference herein.

[0069] A typical commercial aircraft is airborne between 9 and 12 hoursdaily so approximately 1515 (568×(24/9)) equipped aircraft are necessaryto provide complete domestic coverage with one cellular pattern aroundthe clock. Allowing a factor of ⅓ for mismatched schedules and aircraftmaintenance increases this quantity (1515) to 2020 equipped aircraft outof more than 7000 aircraft in the commercial fleet. For coverage in twoor more directions, this number increases although schedule mismatchbecomes less important when overlapping coverage is available.

[0070] Enough aircraft are in flight to provide nationwide domesticcoverage for about 16 hours daily. In most regions, performance islimited between the hours of 1 AM and 5 AM local time when demand isalso low. This coincides with usage of terrestrial cellular systems,which experience peak (busy hour) demand for about 4 hours daily butless than 10% of this level for nearly 10 hours daily.

[0071] Although directional cellular patterns overlap, transmissionsfrom cells in the companion cellular patterns have no more impact onperformance experienced by users in a cell than transmissions fromadjacent cells in the same cellular pattern. Thus, deploying overlappingcellular patterns based on direction of travel does not degradeachievable performance.

[0072]FIG. 6 shows re-use of neighboring or adjacent frequencyallocations within an aircraft for passenger services. Embodiments ofthe invention can additionally provide wireless communications forpassengers on-board an aircraft having identical user equipment as thatwhich supports terrestrial-based users. As previously described, anexemplary aircraft 601 supports its own external coverage cell 603. Asshown in FIG. 6, the aircraft 601 also employs some or all of thefrequency allocations assigned to neighboring and overlapping cells 605,607 and 609 to provide wireless coverage 611 for passengers 613 at lowsignal levels. This approach avoids mutual interference between thisinternal on-board usage and external usage in either direction.

[0073] Within the aircraft cabin 615 shown from a top view, antennas 617mounted internal to the cabin link on-board base station equipment 619with passenger locations 621, enabling passengers 613 to communicate byemploying their user equipment 623. As an example, in the coveragedepiction of FIG. 6, the frequency allocation from cell 605 is reused inthe aircraft cabin. Some commercial aircraft may deploy multipleinternal antennas to ensure coverage for all passenger locations.

[0074] In further embodiments, aircraft can utilize various techniquessuch as low level jamming of terrestrial cellular uplink bands topreclude passengers from using their standard (terrestrial-only)cellular user equipment as airline personnel cannot monitor this usage.

[0075]FIG. 7 shows several sectorizations which differ from typicalterrestrial sectorization through inclusion of a central sector ofcircular shape. Sectorization of ground coverage cells provided bycommercial aircraft divides the frequency allocation given to a coveragecell among the sectors formed therein. This technique can reduceco-channel interference in the cellular patterns supported by theseaircraft. As shown in FIG. 7, for aircraft-based cells 701, severalsectorizations are shown which differ from typical terrestrialsectorization through inclusion of a central sector of circular shape703, 705, 707. Sectorization may divide the annular region into as manysectors as desired and with non-uniform shapes.

[0076] The simplest first configuration 701 employs only two sectors tofacilitate employment of standard cellular technology by limiting sectorsize and, hence, user delay times. Despite its shape and overall extent,the surrounding sector 709 also imposes tighter limits on user delaytimes. The second configuration 711 uses a central sector 705 and threeequal area annular sectors 713, 715 and 717 to reduce co-channelinterference by approximately 3 dB. The third configuration 719 uses acentral sector 707 and six equal area annular sectors 721, 723, 725,727, 729 and 731 to reduce co-channel interference by approximately 6dB.

[0077]FIG. 8 shows the nationwide grid of ground stations 801 thatsupport an exemplary system also set up a cellular pattern to re-use thefeeder link frequency allocation. Each feeder link cell 803, 805, 807,809, 811, 813, 815, 817 and 819 utilizes the entire feeder spectrumallocation. To avoid interference while keeping aircraft antennas andinstallations simple and inexpensive, each ground station uses high gainantennas to track aircraft while exchanging relatively broadband feedersignals. Tracking antennas minimize interference enough to support are-use factor of one for the feeder link frequency allocation therebymaximizing system capacity. With an ample frequency allocation, thisgrid may employ other re-use factors with attendant simplification ofequipment.

[0078] Cells associated with ground stations enjoy fixed locations sothat careful siting of equipment to minimize inter-cell interference orto maximize cell coverage is possible. These cells may employ dimensionssimilar to those employed with moving aircraft-based coverage cells,especially when available frequency allocation for feeder links islimited, but ground station cells and aircraft-based coverage cells areindependent from one another. As long as ground stations provide supportfor each participating aircraft, no relationship needs to exist betweentheir cells and aircraft-based cells.

[0079] Regardless of cell dimensions, cells associated with groundstations do not occupy aircraft coverage cells per se; instead thelatter cells sweep past fixed ground station cells as individualaircraft come and go. With as many as four overlapping directionalcellular patterns, each ground station supports at least four aircraftsimultaneously.

[0080]FIG. 9 illustrates support of multiple directional cellularpatterns. To support four directional cellular patterns, each groundstation cell 901 has sufficient resources 903 to support northbound 905,eastbound 907, southbound 909 and westbound 911 aircraft. As any ofthese aircraft may cross paths as seen from this ground station, whenreporting to the same ground station aircraft traveling in differentdirections share this feeder link frequency allocation, e.g., eachaircraft takes one-quarter of it.

[0081]FIG. 10 illustrates use of high gain tracking antennas at a groundstation also allows for partial re-use of any of the four directionalfrequency allocations within a ground station's coverage area 1001. Thissegmentation requires more equipment 1003, 1005 at a ground station, butalso provides additional capacity by recovering passenger-originatedtraffic from both aircraft. Thus, multiple (co-directional) aircraft1007, 1009 can operate within this coverage area provided they share (inany partition from 0%/100% to 100%/0%) the frequency allocation intendedfor aircraft-based cellular communications. The control center adjuststhe overall cellular pattern for this direction to accommodate anydistortion in coverage attributable to this resource sharing.

[0082]FIG. 11 illustrates handover traffic and control information fromone ground station to another to maintain connectivity for users asindividual aircraft fly along. An aircraft 1101 using feeder link 1103to communicate with ground station 1105. As this aircraft reachesposition 1107 and begins to exit the coverage provided by ground station1105, it continues to communicate with this ground station using feederlink 1109 but also simultaneously establishes a feeder link 1111 withground station 1113. With feeder link 1111 operational, the aircraft1107 switches traffic to feeder link 1111 and discontinues feeder link1109. As the aircraft reaches position 1115, it relies entirely onfeeder link 1117 to communicate with ground station 1113.

[0083] It should also be noted that as the aircraft moves along andperforms maneuvers, e.g. banking, the coverage pattern, the celllocations and size, will modulate. However, adequate margin in thecoverage pattern will accommodate this coverage modulation. In addition,the modulation format can have an effect on the optimal coveragepattern. For example, time division multiple access (TDMA) will restrictthe allowable cell size as a consequence of the moving cell antennawithin the aircraft.

[0084]FIG. 12 illustrates and exemplary method 1201 of providingaircraft-based wireless communications service. At step 1203, aplurality of aircraft are provided each including on-board equipment forsupporting wireless communications with one or more dual mode handsetsand for exchanging wireless communication traffic and controlinformation. At step 1205, one or more ground stations are providedcommunicating with the plurality of commercial aircraft using feedercommunications links exchanging the wireless communication traffic andcontrol information and providing interfaces with a terrestrialtelecommunications infrastructure. At step 1207, a control center isprovided that manages the one or more ground stations and the on-boardequipment of the commercial aircraft and dynamically assigns resourcesto the on-board equipment of the plurality of aircraft using anoverlapped set of coverage patterns. The basic method 1201 can bemodified consistent with the exemplary system detailed above.

[0085] This concludes the description including the preferredembodiments of the present invention. The foregoing description of thepreferred embodiment of the invention has been presented for thepurposes of illustration and description. It is not intended to beexhaustive or to limit the invention to the precise form disclosed. Manymodifications and variations are possible in light of the aboveteaching.

[0086] It is intended that the scope of the invention be limited not bythis detailed description, but rather by the claims appended hereto. Theabove specification, examples and data provide a complete description ofthe manufacture and use of the apparatus and method of the invention.Since many embodiments of the invention can be made without departingfrom the scope of the invention, the invention resides in the claimshereinafter appended.

What is claimed is:
 1. A system for providing an aircraft-based wirelesscommunications service, comprising: a plurality of aircraft eachincluding on-board equipment for supporting wireless communications withone or more dual mode handsets and for exchanging wireless communicationtraffic and control information; one or more ground stationscommunicating with the plurality of commercial aircraft using feedercommunications links exchanging the wireless communication traffic andcontrol information and providing interfaces with a terrestrialtelecommunications infrastructure; and a control center that manages theone or more ground stations and the on-board equipment of the commercialaircraft and dynamically assigns resources to the on-board equipment ofthe plurality of aircraft using an overlapped set of coverage patterns.2. The system of claim 1, wherein the wireless communications service iscellular-type service.
 3. The system of claim 1, wherein the feedercommunications links use standard cellular communications.
 4. The systemof claim 1, wherein the wireless communications links employ standardcellular communications but operate in frequency bands not allocated toterrestrial cellular systems,
 5. The system of claim 1, wherein one ormore of the plurality of aircraft each include an on-board jammingsystem for jamming of terrestrial cellular bands to prevent passengersfrom using terrestrial cellular equipment while in flight.
 6. The systemof claim 1, wherein two or more of the plurality of aircraft eachinclude equipment for crosslinks between the so equipped aircraft forexchanging user traffic and control information.
 7. The system of claim1, wherein the one or more ground stations are collocated withterrestrial cellular sites.
 8. The system of claim 1, wherein thecontrol center is ground-based.
 9. The system of claim 1, wherein thecontrol center is satellite-based.
 10. The system of claim 1, whereinthe overlapped coverage patterns comprise a set of cellular patterns.11. The system of claim 1, wherein the overlapped coverage patterns arebased on primary aircraft direction of travel.
 12. The system of claim1, wherein the feeder communications links operate at microwave ormillimeter wave bands.
 13. The system of claim 1, wherein the feedercommunications links utilize cellular-type communications.
 14. A methodfor providing an aircraft-based wireless communications service,comprising the steps of: providing a plurality of aircraft eachincluding on-board equipment for supporting wireless communications withone or more dual mode handsets and for exchanging wireless communicationtraffic and control information; providing one or more ground stationscommunicating with the plurality of commercial aircraft using feedercommunications links exchanging the wireless communication traffic andcontrol information and providing interfaces with a terrestrialtelecommunications infrastructure; and providing a control center thatmanages the one or more ground stations and the on-board equipment ofthe commercial aircraft and dynamically assigns resources to theon-board equipment of the plurality of aircraft using an overlapped setof coverage patterns.
 15. The method of claim 14, wherein the wirelesscommunications service is cellular-type service.
 16. The method of claim14, wherein the feeder communications links use standard cellularcommunications.
 17. The method of claim 14, wherein the wirelesscommunications links employ standard cellular communications but operatein frequency bands not allocated to terrestrial cellular systems, 18.The method of claim 14, wherein one or more of the plurality of aircrafteach include an on-board jamming system for jamming of terrestrialcellular bands to prevent passengers from using terrestrial cellularequipment while in flight.
 19. The method of claim 14, wherein two ormore of the plurality of aircraft each include equipment for crosslinksbetween the so equipped aircraft for exchanging user traffic and controlinformation.
 20. The method of claim 14, wherein the one or more groundstations are collocated with terrestrial cellular sites.
 21. The methodof claim 14, wherein the control center is ground-based.
 22. The methodof claim 14, wherein the control center is satellite-based.
 23. Themethod of claim 14, wherein the overlapped coverage patterns comprise aset of cellular patterns.
 24. The method of claim 14, wherein theoverlapped coverage patterns are based on primary aircraft direction oftravel.
 25. The method of claim 14, wherein the feeder communicationslinks operate at microwave or millimeter wave bands.
 26. The method ofclaim 14, wherein the feeder communications links utilize cellular-typecommunications.